Since their earliest introduction, typewriters have had ribbons which were replaced by the operator as needed. When the ribbon was worn out, the typewriter operator would remove the supply and takeup spools and the used ribbon wound about them from the typewriter. This was often a very dirty and messy task because the ribbon was laid bare to the operator. Because of this shortcoming, ribbon cartridges were developed for use on the typewriters. Ribbon cartridges were enclosed units having a supply hub, a ribbon pancake wound about the supply hub, and a takeup hub enclosed within a case. The operator was not likely to become dirty when changing the typewriter ribbon because it was almost totally enclosed within the case. Thus, changing the typewriter ribbon became a relatively neat and clean operation.
One drawback of the cartridges was that the entire cartridge, including the case, was thrown away once the ribbon was exhausted. This practice was economically acceptable so long as plastic materials from which the cases were made were cheap and the labor costs involved in producing the cartridges was low. However, with the rising cost of raw materials and the greatly increased costs for transportation and labor, these replaceable cartridges have become a relatively expensive aspect of modern office operations.
One way to reduce the costs involved is to replace the worn out ribbon within the cartridge with new, fresh ribbon. One way to do this is to ship the used cartridges back to a commercial facility where the sealed cases can be opened and the used ribbon replaced with new, fresh ribbon. This is presently being accomplished on a commercial scale. Another method to replace the ribbon is to have the operator replace the ribbon in the cartridge without the need for sending the entire cartridge back to a recharge facility. A cartridge designed for accomplishing this is disclosed in U.S. Pat. No. 3,260,344 to Doyle. This solution, however, merely reintroduces one of the original drawbacks of typewriter ribbons. The operator must contend with the messy, dirty, exposed typewriter ribbon within the case much in the same manner as the operator was exposed to the dirty typewriter ribbon in the typewriter.
One limitation of operator recharged cartridges is that cartridges of the type which have gears used to advance the ribbon are not suitable for operator replacement. This is because the gears generally get dirty during use and must be cleaned between each recharging for optimal performance. Further, gears and other moving parts may require selective replacement. These tasks are best provided by a recharge facility and are not truly suitable for performance by the operator. However, cartridges of the type which incorporate no gears or other moving parts, except for the rotating hubs and the moving ribbon, such as the ribbons used in IBM "Selectric" typewriters, are quite suitable candidates for operator replaceable ribbons. However, heretofore rechargeable cartridges have been unacceptable for operator replacement of the ribbon because of the lack of means for shielding the operator from the dirty ribbon.